An electronic nose or artificial olfactory system is a device that is capable of detecting a wide variety of analytes in fluids such as vapors, gases and liquids. The device comprises an array of sensors that in the presence of an analyte produces a response, such as an electrical response. The device produces a unique signature output for a particular analyte. Using pattern recognition algorithms, the output signature can be correlated and compared to a particular analyte or mixture of substances that are known. By comparing the unknown signature with the stored or known signatures the analyte can be identified.
Current commercially available sensors can be used for a variety of applications. These commercial applications include, but are not limited to, environmental toxicology and remediation, biomedicine, such as microorganism classification or detection, material quality control, food and agricultural products monitoring, heavy industrial manufacturing, ambient air monitoring, worker protection, emissions control, and product quality testing.
Although in some instances, an electronic nose is sufficient to accurately determine the analyte of interest, other physical data within the environment of the analyte go undetected. These additional data can be used to identify the analyte. Physical parameters of the analyte include, but are not limited to, temperature, humidity, color, pH, solution concentration, wavelength absorption, taste, vapor pressure, mass, pressure, optical density, magnetic field, etc. By measuring these physical parameters in conjunction with electronic nose data, a more accurate assessment of the analyte and its surrounding environment can be accomplished.
For example, the current state of the art breathalyzer used to determine the blood alcohol content includes an infrared detector (IR). In certain instances, IR detectors are susceptible to interferences from other volatile organic compounds (VOC) which also absorb the IR, (see, Jones A W, J. Anal Tox. 20:522-527 (1996)). Manufacturers of these evidentiary instruments have responded by adding additional channels in an effort to differentiate between the IR signature of ethanol and other volatile organic compounds. These volatile organic compounds include acetone, toluene, xylene, methanol, isopropanol, and acetaldehyde, the list also includes water, carbon monoxide and carbon dioxide. Concentrations of the other analytes in the test gas are generally in the range of 0.01 to 0.10 mg/L. However, these modification are still ineffectual.
Hybrid sensor systems containing different types of chemical sensors are known. For example, a system known as the MOSES system exists wherein a modular system was used that included an array of different semiconducting gas sensors based on metal oxides, polymer coated quartz microbalance sensors, calorimetric sensors and electrochemical sensors. The MOSES system optionally contained a semiconductor field effect transistor sensor (MOSFET). The system is limited to detecting odors using chemical sensors (see, H. Ulmer et al., Sensors and Actuators B, 43, 24-33 (1997)).
In addition, U.S. Pat. No. 5,801,297, which issued to Mifsud et al., on Sep. 1, 1998, also discloses a hybrid chemical sensor system. This system includes a first enclosure having a first detection means wherein the first detection comprises a plurality of gas sensors using a same first technology selected from semiconductor gas sensors technology, conductive polymer gas sensors technology, or acoustic surface wave gas sensors technology. The system also includes a second enclosure having a second detection means. The second detection means includes a plurality of gas sensors using a same second technology selected from semiconductor gas sensors technology, conductive polymer gas sensors technology, or acoustic surface wave gas sensors technology. In this system, the second technology is different from the first technology.
In another hybrid sensor system, a combination of an electronic tongue and an electronic nose is described. In this system, the electronic nose consisted of an array of gas sensors with pattern signal handling capability and sensor pattern recognition algorithms. The electronic tongue consisted of taste analysis of liquids based upon pulsed voltammetry. (see, F. Winquist et al., Sensors and Actuators B 58, 512-217 (1999).
Moreover, U.S. Pat. No. 5,832,411, which is issued to Schatzmann, et al., on Nov. 3, 1998, discloses a plurality of sensor units distributed over an area that communicate via a network with a central monitoring unit. The sensor units include sensor arrays that provide them with raw data in response to the presence of selected compounds in the ambient fluid. The raw sensor data is then processed to compute a local profile. The local profiles from the individual sensor units are then used to compute a spatial and temporal map for the compounds in the fluid. This map can then be used for a variety of purposes including tracking and predicting the flow of compounds through the area, identifying the source of compounds in the area, monitoring abatement, and controlling industrial processes.
In view of the foregoing, what is needed in the art is a system that can capture both physical data and chemical data in a particular environment, especially a networked environment. A system is needed which can respond to a combination of a chemical stimulus and a physical stimulus. The responses can be stored and analyzed and thereby identify the analyte of interest. The current invention fulfills these and other needs.